Blocks having specific interrelationships are well known and have been described for educational uses. See, for example, the U.S. Pat. No. 3,208,162 to Wisdom wherein a square and cube root demonstrator is described. The U.S. Pat. No. 595,782 teaches a block model wherein a unit cube is divided into particular volumetric fractions such as a third, two thirds and the like. Several trigometric relations can be illustrated with the blocks. The block construction described by Randolph in U.S. Pat. No. 3,645,535 describes various relationships between a tetrahedron, cube, and an octahedron and adapting these in a block system. Various polyhedra are shown in a publication by Coxeter entitled "Introduction to Geometry", published by Wiley and Sons, and in a book entitled "Shapes, Space and Symmetry" by A. Holden, published by Columbia University Press in 1971.